Compression-rheostat.



E. L. CLARK.

COMPRESSION RHEOSTAT.

APPLICATION men NOV. 15. 1915.

Patented Oct. 24, 1916.

2 SHEETS-SHEET 2 EMEH 5 UN L. CLARK Mm W 1 M,

UNITED STATES PATENT OFFICE.

EMERSON L. CLARK, 0F LAKEWOOD, CHIP, ASSIONOB TO NATIONAL CARBONCOMPANY, A CORPORATION OF NEW JERSEY.

COMPRESSION-RHEOSTAT.

Specification of Letters Patent.

Patented Oct. 24, 1916.

Application filed November 15,!915. S erial No. 61,451.

sistance of the elements when placed under variable pressure.

One of the objects of this invention is to secure rapid and ellicientradiation of the heat generated with a simple construction of rheostat.

Another object, of my invention is to increase the range through whichthe resistance may be varied.

further object of my invention is to prevent arcing at the points ofsupport."

Another object is to provide means for transmitting pressure uniformlyover the contact area of the resistance plates.

In the present type of compression rheostats the resistors usuallyconsist fa number of plates of carbon or other composition suitablysupported with the jfaccs in contact. 'hen it is desired to increase therange of a rheostat of this type. theordi nary method is to increase thenumber'of plates. ltisfound, ho\\'ever, that the range;

is not increased in the same. proportion as the number of plates and theincrease in the "nun'iher of plates beyond certain limits-- is entirelyimpractical. Thisis d'uetto the fact that if a long horizontal pile ofsurh: resistors. compressed to the-point of lowest resistance. isgradually relieved 'trmn. pres sure, the resistors at the end'atwhichpressure is applied are almost. entirely relieved from pressure andslide readily along the support. Those at the other e| d.,however,

are always under some compression. because.

in order to expand they must, overcome the frictional resistance of allof the platesrestin edgewisc on the supports; '.\\'ith a rather longpile, in many cases the circuit fore the contact. resistance of theplates at the tear end is appreciably increased. To

\\/ill be opened at the compression end heeliminate this diszulvautageand secure a wide range with a rclativelyshort, rhcostat,

an aitrangement for overcoming the frictional resistance will e used toincrease the upper limit of resistzhceaud a mechanism for placing thesections in parallel will be used to obtain a low resistance.

Other features of the construction are shown in the drawings and set;forth in the description in which Figure 1 is a plan view of my improvedrheostat. Fig. 2 is a side view of Fig. 1. Fig. 3 is a cross section ona reducedscale on the irregular line of Fig. 1. Fig. i is a detail viewof the plate used at the pres sure ends. Fig. 5 shows a partial crosssection'on the line B-B of Fig. 1. Fig. 6 is a partial, cross section ofthe platesv and supv port at the central point of support. .Fig. 7

is a detail view of one of the plates used bc-' tween the sectio'ns andas a contact plate. Fig. 8 is a view partially nrsection illustratingthe" position of certain members when the sections of the 'rheostat' areIll se|'ies. Fig. 9. is a \"ie w similar to Fig. 8 showing the samemembers when thc. sections are in parallel. Fig.1t) shows anarrangeinent formaintaining'the contacts of 'tlie series-paral'lelswitching device in earta i n positions.

Referring particular-1y. to Fins. 1. and

of the drawings. the frame of the-rhcostatcons sts. of two end members 1and-'2. preferably of metal; oined by side rods Band -I and h) ;\.rod 5helow and betweenthe side rods. .Thesi rods preferabl v consist offal.

body portion'ti ofq netal (.Figfs and 6) covered with 1a coating 7.ofvitreous etn\mcl or' other insulating. material. The end sfo'fthesrods are fastened.tonn-dinsulated from the. end members. for'exaniple by. nieaus'ot insulating bushings t and nuts 9 threaded overthe endsof the rods wliich'are of .re-

din-ed eroei'scetion. p a a flint-plates 10 of the '1'lieostat.are-prefeliahly 'ci rcnlarand fare shigg'crcd .to provi' erailiatiligxfins. This is donc'hy plncingthe plates'sotlmt they all restupon the central M rod 5 with'ieaclralternate one. touching the sid rodsilandyl rcslwctivcl v. Bysnitably choosing the diameter of the. dslfsandthe s'paeiugof-thc supporting rods, that part of il ltfltllfikhengaged in radiation ofpheat may ho suitably proportioned. Asatisfactory re.- lation lit-tween the-two shown in Fig. 3 i ll. \\'llit'll the portion of thedisksxconstitub ing the resistance is showniiisection. Atl- 35 plate 9.3.

jacent the erid 1 of the rhcostat is placed an insulating block 11 ofthe shape shown in Fig. 4 and also a metallic contact plate 12 as shownin Fig. 7, both of which are suit- 5 ably formed to rest upon the rods3. 4 and 5.

Near the end 2 another insulating block 11 and contact plate 12 aresimilarly mounted on the supporting r'ods. Phe arrangement for applyingpressure consists of a metal plate 13, a ball H adjacentthereto. asocket 15 for retaining the hall. and a frame 16 adapted to retain thehall and socket. The frame 16 and plate 1 3 are attached to theinsulating mieinlier l2 by means of screws 17.

15 Pressure is applied by means of a hand wheel 18 on a screw 19threaded through a bearing 20 in the end plate 2. The end of the screw19 is fastened to or made integral with the socket lai and is reduced tolit into 20 a slot 21 in the frame 10.

The resistance disks are divided into a number of sections by means ofintermediate latcs which may have the form shown in I ig. 8. In thedrawing two plates '2'). 23.

25 dividing the rheostat into three units. are

shown by way of example. although a larger number of units mav'heprovided. 7

The means for diminishing friction of thc disks on the supports consistsof the following arrangement. To limit the movement of openingthecircuit. The disks in the intcrmediate unit will be similarly packed.Each of the stops has a means. such as projecting hook 27, to engage oneend of a 1 spring 2s which passes through openings in the stops, theother end being fastened in any suitable manner to a n'ojection 39 ofthe intermediate plates, or example by means of strips 30 shown in Fi 7.

The means by which the sections may he placed in series or in parallelconsists of two conducting rods 31, 3:? on opposite sides of the.rhcostat, which pass through insulating bushings 9 in the end platesand provide terminals 34. 35' to which leads may he secu'rcd in anydesired way. Electrical connection is made between the terminal rodson't'he one hand. and end contact plates 12,

or .d,

'12 and intermediate plates 23 on the other. by means of spring clips36, 37. 38

and 39 respectively (Fig: 1). Thcse clips gi ip, tlie rods in the mannershown fully in Figs. 8 and 9; v

Each of the clips is connected by means of a flexible conductor orpigtail 40 to a projection 41 (Fig. 7) of the contact or in- 1,2o2,1e1 Itermediatc plates. To permit the spring clips 36 and 37 to he movedsimultaneously, they are fastened to a har and clips 38 and 3!) aresimilarly fastened to a har -13. The rod 3'. is cut away on diagonallyopposite faces at the point where the clip 36 grips the rod and at eachof these cut away surfaces an insulating segment 4-1 is at.- tached. asshown in Fig. 8. The position where clip 39 grips the rod is alsoinsulated in the same manner at two points of its circumference. Theshape of the clip is such that in the position shown in Fig. 9 it isinsulated from the rod and by rotating it ahout 60 degrees around thecontact bar it is in electrical contact therewith.

spring 45 is fitted to each of the insulating bars 43 and cooperateswith flat portions 46', 47 of the conductive rods to maintainthc clipsand bars in either of the two operating positions.

The rheostat may e manipulated in the following manner:\\'hen the handwheel 18 is turned the pressure is transmitted to the disks through thehall and socket joint described. .\s the disks are moved the plates 22.23 arforced back from the stops against the pressure ofthe springs 28which have no special function during this part of the operation. Theresistance of the r h'costat is thus decreased by compressing'thetlislcin much the same manner as in prior types. However, the ope 'ationof the rheostat dun ing the reverse movement of the hand wheel isdecidedly dill'erent from that of prior types. In such prior types thedisks near the eolnpression end will readily slide along the supports.but before those at the other end can expand it is necessaev to overcomethe friction of all the rest of the disks on their supports. T hefrictional resistance to expansion therefore progressively increases invalue toward the stationary end. Most ofthe disks thus remain underconsiderable pressure, especially in long piles. ,In cutting inresistance with my improvement, however. the disks in the first instanceare forcibly moved along by the first set of springs. so that the disksin the second and third sections are relieved of the frictionalresistance of the first set. The second set of springs likewise forciblymoves the disks in the second section, which relieves the "disks in thethird section of the correspond- 'ment therefore permits a rhcostat to hmade of any desired length by adding with each additional section a setof springs and its coiiperatmg parts.

While for purpose of illustration I have shown only two sets of springsin a three section rheostat, it will be apparent that any number may beadded to produce any desired length of rheostat.

To further increase the range beyond that of the spring device,especially to decrease the resistance below thatof all the sections inseries when under compression, a simple arrangement is used to place thesections in parallel. To place thesections all in series the insulatingbar 4'2, is turned to the position shown in Fig. 8 and the opposite bar43, clip 37 and insulation 44 are also placed in similar electricalrelations. The intermediate plates 22, connected to clips 36, 39, arethus insulated from the bars 31, 32, and current passes from terminal 34to clip 37, to front plate 12, through all the sections in series torear plate 12, to clip 38, and thus to terminal bar 35. v

\Vhcn it is desired to place all the sections in parallel the bars 42,43 are turned through an angle as illustrated in Fig. 9 to cause theclips 36, 39 to conductively engage the bars 31, 32. Clips 37, 38 remaincontinually in contact because no insulation is used at their points ofcontact with the bars. The circuit of the unit betweenstiitioi1ii'y,'c1id land plate 2:2 is from clip 38 on bar 35 to't'he plate 12,through the disks of theiinit to plate 2:2

and to clip 36 on bar 34. The unit between the plates .22 and 23 iscoiinectedliyclip 3!), to bar 35, and by clip 36. to bar 34. By means ofclip 39 and clip 38 the third unit is connected across tlie terminalbars, so that parallel across all .three units are thus in bars 34. 35.

The detail view-of Fig, 6 shows a method" of preventing arcing at thepoint of contact of the edges of 1 18 disks, which 'wonldin,

time destroy the insulation of the support either on oneor both edges so1 iat no are can occur at the peri 'ihery oftlie disks close to thepoint .of support. Therbeveling is only required at thepointo'fsupportmn rod 5, but the: disk is preferablv .bevel'ed' allaround its periphery so that n o='special care is required in placingthe-disks in positio i.

The staggered disks and rod supports pro-- \ideasimple method ofsecuring-agood radiation because the passagccof cooling air between thepro ecting surfaces .IS unmi-' peded. Renewals maybe readily made withthis arrangement and the elements are selfa'lining.

' Having described inventiomwvhat- I claimgxs:

1. In electric rheostats, a frame comprising en'd members and sidemembers, a pli irality of disks eachhavingits surface in partial contactwith the adjacent disks, and

means. for maintaining alternate disks adjacent difierent side members,whereby a ance portion.

compression force.

-plurality of disks constituting a members connecting said end members,a

member intermediate to the side members, a plurality of disks alined bythe intermediate member and one of the side members, a plurality ofdisks alined by the intermediate member and the other side; member,alternating with said first mentioned disks, and means for applyingpressure to the disks.

3. In electric rheostats, end members, side rods connecting said ends. arod intermediate thereto, a plurality of disks forming a pile, saiddisks being alternately placed in contact with the opposite side rodsand the intermediate rod with the faces partially in contact, and meansfor applying pressure to the contact area.

4. In electric rheostats, oppositelyplaced vertical end members,horizontal side rods connecting the and members, a rod intermediate tothe side rods, a plurality of circular trod and the other side rod andalternating with the first mentioned disks whereby a portion .of eachdisk servesas a resistor and [the remainder serves as a radiating-fimandmeans for applying pressui'e'to t e resist- In an electric rheostat, aplurality of disksconstitfuting a pile, compression means,and.ineansfor.movinga section of the pile bodily toward the-compressingend .as the compressing force diminishes. whereby the adjacent sectioncan expand without'nwving the. first mentioned section;

6. In. an elec'tric rheostat, a plurality of disks constituting a'pile,means 1 0r dividing the pile'into a" plurality of sections; compressionmeans. and means cooperating with the first mentioned means to opposethe coinprcssioir force and adapted to'move a section of ,the rhcostatin'tlie' opposite direction as the compressing force diminishes. where;

by the adjacent section is icr nitted to .ex-

pa id as a simple rheostatt' the same length as the section;

T; In an electric i-IicostaLmid n'icmbers. a pl-ural'ityof disksconstituting a pile, means for dividing the pile into a plura ity ofsec- 'tions, side rods connecting saiiiheinl incin- .-bers, meansfor-applyi i pressure to the pile, and aspi'ing attachet to said firstllltlb.

ti'oned means and said 'rod, opposing the 8. In an electric rheostat,end members, side rodsj connecting said-end members, a ile. means fordividing the pile into a plura ity of sections, compression means, astopconnected to one of said rods anda spring connected ill between saidfirst mentioned means and said stop, adapted to oppose the compressionforce and move said first mentioned means against the stop.

9. In an electric rhecstat, end members, side rods connecting said endmembers, a plurality of disks constituting a pile, means for dividingthe pile into a plurality of sections, compression means, adjustablestops attached to the rods and springs connected between said firstmentioned means and said stops, said springs opposing the compressionforce and adapted to move said dividing means and sectipn adjacentthereto, whereby the section on the opposite side of said dividing meansis permitted to expand without moving the first mentioned section whenthe compression is withdrawn.

10. In an electric rheostat, endmembers, side members connecting the endmembers, an intermediate member, a plurality of disks placed alternatelyon opposite sides of the intermediate rod but partially in contact,means for dividing the rheostat into a plurality of sections,compression means and means for moving a'section as'the compress ingforce diminishes, whereby the adiacent scctioncan expand withoutdisplacing sa-id first mentioned section.

11. In electric rhcostats, end members, a plurality of disks forming apile between said ends: means for dividing the pile into a plurality ofsections, a conducting rod, and meansfor electrically connectinganddisconnecting the dividing means and the rod.

12. In electric rheostats, end members,.a ilurality of disks forming apile between said ends, means for dividing 'the'pile into a plurality ofsections. a conducting rod, an insulatipg member attached thereto andmeans connected to said dividing means and adapted to contactalternately with said conducting rod or insulaitng' member.

3. In electric rheo'stats, .end members,.a plurality ofdisks forming apile between said ends, means plurality of sections, a cylindricalconducting rod having insulating segments attached thereto. a springclip litted on the rod and adapted to be rotated relatively thereto, anda flexible connection between said clip and dividing nu-ans. Q

14. In electric rheostats, end members, a plurality of disks forming apile between sion plate, for dividing the pile into a "signature.

said ends, a metal plate for dividing the pile into sections, acylindrical conducting rod having insulating se ments attached thereto,a spring clip tte on the rod and adapted to be rotated on the rod tocontact either with th conductive parts or the-insulating segments ofthe bar and a flexible conductor connecting the plate and clip.

15. In BlQCtI'IQI'l'lEOStHtS, end members, a plurality of disk? forminga pile between said ends, a plurality of metal plates between said disksdividing the pile into sections, two conducting rods connecting saidends having insulating segments thereon, a plurality of spring clips oneach of said reds, flexible connections between said plates and said'rods and means for rotating the clips on the rods.

I 16. In an electric rheostat, a frame comprising end members and sidemembers, a compressible pile between said ends, a compression plate forthe pile, a ball adjacent thereto, a threaded rod passing through one ofthe ends and having a retaining socket for the ball.

17. In an electric rheostat, a frame comprising end and side members, acompressible pile between'said ends, a. compression plate, a balladjacent thereto, a retaining socket member for the ball, a threaded rodpassing through the end and connected to the socket; member, and a handwheel for turning the rod to apply pressureto the pile.

18. In electric rheostats, a frame comprising end members and sidemembers, atompressible pile between said ends, a compressionplate, aball adjacent thereto, a socket member for the ball, a threaded rodpassing the compression plate and the compression rod'for moving saidplate with the rod.'

19. In electric rhoostats,,a frame compris'. ing end members and sidemembers, a compressible' pile between said ends, a compresa halladjacent thereto, a socket member for the ball, a threaded rod p'assingthrough .an end member and connected"to the socket, andaframe fastenedto said plate adapted to engage said rod whereby the compression plateis moved back and forthwith the compression rod.

In testimony whereof I hereunto ailix'my 'nMnnsoN CLARK.

